The difference in electrical pressure (voltage) between any two points in an electrical system or between any point in an electrical system and the earth.
Differential
Having different effects or results. The difference between two consecutive values.
Differential gear
A certain arrangement of gears connecting two axles in the same line and dividing the driving force between them, but allowing one axle to turn faster than the other. Often used in the rear axles of automobiles to allow a difference in axle speed for turning curves.
Differential leveling
Using a level and rod to determine a difference in elevation between two points.
Differential pressure
Pressure difference in two parts of a system or two areas.
Differential thermostat
A type of automatic thermostat (used on solar heating systems) that responds to temperature differences (between collectors and the storage components) so as to regulate the functioning of appliances (to switch transfer fluid pumps on and off).
Differential-acting hammer
Type of machine for driving pilings, which uses air or steam to drive the hammer.
Diffraction
Energy redistribution due to an obstruction or change in the surface over which it is passing. Diffuse 1. To pour in different directions. (2) Spread out or dispersed, not concentrated.
Diffuse solar radiation
Sunlight scattered by atmospheric particles and gases so that it arrives at the earth's surface from all directions and can not be focused.
Diffuser
(1) A device that distributes light evenly. (2) HVAC air outlet, which directs air widely in a fan-shaped pattern.
